Clean Water and Sanitation (SDG 6), Climate Action (SDG 13)
Investigating ball-milled silk fibroin film powder as a potential adsorbent for wastewater remediation Kgomo H * , Dube S., Nindi MM Department of Chemistry, University of South Africa, Corner Christian de Wet and Pioneer Avenue, Florida Park, South Africa Pharmaceuticals and/or their metabolites have been increasingly detected in the aquatic environment including wastewater, surface water (including rivers, lakes, and coastal waters) and groundwater. Though the concentrations of the PhACs in the environment are at trace levels, their regular and continued release due to increasing and extensive usage is a serious concern. Moreover, the PhACs do not exist as individuals in the environment but rather as a complex mixture that could lead to undesired synergistic effects that can exert stronger toxic effects than exposure to a single one. Since conventional technologies for water treatment have been shown to be inefficient for the complete removal of PhACs from water, other techniques have been explored including advanced oxidation processes (AOPs), advanced filtration techniques, and adsorption processes amongst others. These have generally shown better removal and/or degradation efficiencies of PhACs compared to conventional techniques. Though effective, a shared concern among researchers is related to intermediates generated during the processes, some of which are persistent and more toxic than the parent compounds. As a result, adsorption is usually the preferred method due to its wider applicability, relatively low costs, and limited generation of undesirable by-products. Natural bio-based materials have been mostly preferred over synthetic materials since they are biocompatible and biodegradable after use. Adsorbents derived from chitosan, moringa, clays, and agricultural wastes have been explored as potential adsorbents for the removal of various PhACs. This work presents the prospect of utilizing silk fibroin as a potential biomaterial for fabricating low- cost adsorbents for the removal of multiclass pharmaceuticals from the aqueous environment. The silk adsorbent was derived from wild silkworm cocoons of Argema mimosae, a species indigenous to Africa. Following the successful degumming of the cocoons to obtain the fibroin, various solvent systems were investigated for dissolution. The resultant silk fibroin solutions were cast to obtain silk films which were characterized to investigate any processing-induced effects. Thereafter, the films were ball milled to obtain silk powder, which was characterized using FTIR, SEM, XRD and the particle size distribution was estimated using DLS measurement. Finally, batch adsorption studies were carried out under different operating conditions including pH, temperature, and contact time. The experimental data were fitted to the pseudo-first-order and pseudo-second-order kinetic models. The Langmuir, Freundlich and Temkin isotherm models were also applied. The performance of the adsorbent in a complicated matrix such as wastewater influent and effluent was investigated.
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